A modification of this type is seen in the parasite Drilophagus, where the unci and rami are two-pronged at the end, but the trophi are not movable on one another, but protrusible as a whole to serve as an organ of attachment to the Oligochaete Lumbriculus, to which this Rotifer attaches itself. See Vejdovsky, "Ueb. Drilophaga bucephalus," etc., in SB. Böhm. Ges. Jahrg. 1882 (1883), p. 390.
"Zur Rotatorien Württemburgs," in Jahresb. Ver. Würt. vol. l. 1894, p. 57.
Similarly Hudson and Zelinka both regard the dorsal antenna as formed by the coalescence of two antennae. These retain their distinctness in Asplanchna; in some Bdelloida the single antenna is supplied by a pair of nerves.
C. R. Ac. Sci. cxi. 1890, p. 310; cxiii. 1891, p. 388.
Acta Univ. Lund. xxviii. 1891-92.